(a) Field of the Invention:
The present invention relates to a focal plane shutter made to open and close an exposure aperture by operating a plurality of blades made of opaque laminar materials.
(B) Description of the prior art:
In this type of focal plane shutter, a plurality of laminar blades operatively connected with one or two arms are usually so arranged as to be housed as overlapped when retreating from an exposure aperture and to develop to close the exposure aperture as slightly overlapped with adjacent blades when covering the aperture and two blade groups each having a plurality of such blades as a set are provided, one of the groups is used to open the shutter and the other is used to close it.
It is needless to say that, in this type of focal plane shutter, in case one blade group covers the exposure aperture as mentioned above, the amount of the overlap of the adjacent blades with each other is desirable to be larger for the reason of preventing a light leakage. However, in order to thus increase the overlap between the respective blades, the width of each blade itself must be necessarily made larger. If the width of each blade is made larger, the area occupied by one blade group when it is housed or folded will become so large that it will be difficult to make the shutter device smaller and, as a result, it will be impossible to equip a small camera with this kind of focal plane shutter. In other words, in order to make this kind of focal plane shutter smaller, the width of each blade can not help being made smaller but, if it is made so, the amount of the overlap with each blade when the blade group is developed will become smaller and, as a result, the light will be likely to leak.